1. Field of the Invention
The invention relates to collection containers, such as collection containers used for collecting specimens of bodily fluid.
2. Description of the Related Art
Tubes are used to collect specimens or samples of bodily fluid. The typical tube includes a cylindrical sidewall with a spherically generated closed bottom and an open top. A closure is mounted to the open top to permit sealing of the tube. The closure typically comprises an elastomeric stopper that is urged into the open top of the tube. The closure also may include a rigid plastic member that retains the elastomeric stopper. The plastic member can be used to manipulate the stopper for placing the closure in the open top of the tube or for removing the closure from the tube. The elastomeric stopper may be formed from a pierceable and resealable material. Some closures also include a layer of foil across the top of the closure for enhanced performance of the closure as a gas or moisture barrier. Tubes typically are formed from either glass or plastic. Glass tubes perform well as gas and moisture barriers, but are more fragile than plastic tubes. Hence, glass tubes may require special handling. Plastic tubes are substantially unbreakable. However, certain plastics may be permeable to gases or moisture.
A sample of fluid collected in a tube typically is sent to a laboratory for analysis. Characteristics of the collected sample may change if the sample is exposed to ambient gases or if vapors produced by the sample are permitted to permeate through the walls of the tube and into the ambient surroundings. Characteristics of the collected sample also may vary after exposure to gas trapped between the surface of the collected fluid sample and the stopper. The volume between the top of the collected sample and the stopper is referred to herein as the head space.
Most laboratory analysis of collected fluid samples are performed with automated or semi-automated equipment. The equipment typically is geared to accommodate tubes of specified outside dimensions. Tubes that are too small may require separate handling, and hence tubes with non-standard outside dimensions may require slower less efficient and more costly analysis of the specimens collected therein. Accordingly, most health care facilities collect specimens in standard sized tubes. However, some tests can be performed with relatively small volumes of a fluid sample. A collection of a small volume sample in a relatively large tube necessarily creates a large head space with a large volume of air above the collected sample. Accordingly, there is a greater probability that characteristics of a small collected sample will vary prior to testing due to interaction or reaction with the relatively large volume of air in the head space.
It is desirable to provide a tube with standard outside dimensions. It is also desirable to collect only the smallest volume of a sample that is required for a particular laboratory analysis. Furthermore, it is desirable to provide a smaller and substantially uniform head space.